1. Field of the Invention
The present invention relates to collision sensors and compliance devices, and in particular to an apparatus suitable for providing an output signal upon collision with an object and permitting limited correction for mechanical tolerances when used on a robotic arm onto which is affixed a robotic hand.
2. Discussion of the Relevant Art
Many types of collision sensors are available and many may be suitable for use with robotic arms and hands presently in use today. Generally, these devices utilize light beams of different types or sonic transducers which are interrupted by an interfering article. Interrupting the light beam provides an indication, via electronic circuitry and cabling to the main control computer that an object has interfered with or interrupted the natural path of the sensing light beam, thereby provoking a particular response or adjustment that is made by the main computer. Although a light beam sensor or one of the sonic type may be suitable for many applications, their generally instantaneous response caused by interruption of their normally focused beam may not be suitable for use by a robotic end effector or arm. With these devices contact with an object need not occur, but only that the beam be broken to invoke a particular response by the main frame computer controlling the automatic operation of the mechanism. Sometimes it is desirable that mechanical contact between the robotic arm and an object in its path occur prior to invoking a response by the computer such as, for example, in a compliance device. This type of contact permits a certain contact threshold to occur prior to activation of the electronic response indicating such contact and this is capable of correcting small mechanical errors in location, such as, for example, that which may occur when inserting a rod into a hole if the alignment is not exact. This may have many advantages in that the threshold may be adjusted to provide the desirable contact pressure or force prior to invoking the subject response.
In many applications a combination of a light or sonic sensor together with a mechanical sensor is desirable. For example, the light sensor may be utilized to determine when an article is in position at its specific location and then a robotic arm together with its associated hand may be used to encompass or pick up the subject article. However, movement of the robotic arm into position may cause contact with articles not in their proper location and it may very well be desirable that the main frame computer be told by means of an electronic signal that there is some mechanical interference with the movement of the robotic hand.
A typical robotic hand for which the present collision sensor is ideally suited is disclosed U.S. patent application Ser. No. 580,175, issued on Feb. 16, 1984 to Mathew L. Monforte, and U.S. patent application Ser. No. 591,265, issued on Mar. 19, 1984 to Mathew L. Monforte.
The present invention overcomes the shortcomings of known devices by being small in size, light in weight and easily adaptable to robotic arms having robotic hands affixed thereon as will become apparent from the description which is to follow. The instant invention may be a unitary structure which includes a robotic hand together with a robotic collision sensor and compliance device or may be an apparatus which may have a robotic hand affixed on one end thereof with the other end being affixed to a robotic arm. Thus, the instant invention is suitable for use with robotic hands presently in use today, and is capable of providing a safety feature for robotic control systems providing an electronic signal to the computer whenever an electronic arm or hand comes into contact with an article appearing in its path.